1. Field of the Invention
The present invention relates to a method for allocating first transmitters, of a tire monitoring system, especially of a tire-pressure monitoring system, having a wheel unit comprising a sensor, a transmitter and a sending antenna, on each of N wheels arranged on L axles of a vehicle according to a predetermined axle formula, further having at least one receiving antenna on the vehicle body associated to the first transmitters, and an electronic receiver and evaluation system, by association to the respective transmitter of an identifier characteristic of a particular wheel, through the emission of data telegrams, which contain the identifier, in response to the triggering action of the trigger transmitters, and by passing on such data telegrams to the central electronic receiver and evaluation system. Further, the invention relates to a device suited for carrying out that method.
The “axle formula” indicates the number of axles provided on the vehicle and the number of wheels at each of the axle positions of the vehicle. “Axle position” is to be understood as the location at which single wheels or a number of wheels, which belong together and are placed side-by-side, are arranged. If there is only a single wheel at a given axle position as is usual with automobiles, then the axle position is identical to the wheel position. In case of trucks, however, there can be provided more than one wheel at a given axle position, e. g. two wheels in case of a truck with twin wheels. In such a case there are two wheel positions at an axle position of twin wheels.
2. Description of Related Art
A method of that kind and a device for carrying out that method have been known and are used for monitoring the wheels of a motor vehicle with respect to certain given values, such as tire pressure, temperature, and the like, for example. Wheel monitoring systems of that kind must be capable of automatically detecting the position of a wheel on the axles, i.e. a mounting position of one or more wheels on a given axle. In the case of passenger cars, normally a single wheel is mounted at each axle position so that the axle position is identical to the wheel position of the respective wheel. In the case of commercial vehicles, however, two wheels (twin tires) may be mounted at one axle position of some vehicles so that two wheel positions are associated to one axle position in that case. For allocating a first transmitter to a defined axle position, one normally uses electronic wheel units that can be triggered and emit their data in response to the receipt of a trigger signal sent out by a second transmitter which is a trigger transmitter.
This is accomplished by the known method and the known device by associating one trigger transmitter to each axle position. During a learn phase, the central electronic receiver and evaluation system drives the trigger transmitters of the respective axle positions so that upon receipt of the trigger signals the electronic wheel unit associated to the driven trigger transmitter sends out its data in the form of a data telegram which is received by the at least one receiving antenna and is passed on to the central electronic receiver and evaluation unit. In order to check the source of that data telegram for plausibility, that process preferably is repeated a number of times. Upon conclusion of that process, the identity of the wheel associated to the triggered electronic wheel unit is known, i.e. its axle position has been learned.
This manner of proceeding allows building-up of a bidirectional transmission path by means of which the transmission time of the electronic wheel units can be determined by a control unit in the central electronic receiver and evaluation system. This clearly reduces the learning times of the tire monitoring system it being now possible to request a plurality of telegrams in rapid succession from each electronic wheel unit, at the beginning of a trip, so that the number of telegrams required for safely determining the correct allocation will be available within a clearly shorter period of time. In addition, when the vehicle is stopped and normal pressure conditions prevail in the tire, the electronic wheel units can remain switched off, which improves the service life of the electronic wheel units.
However, it is a disadvantage of the known method and of the known device that a separate trigger transmitter must be associated to each axle position, i.e. to each single or twin wheel on each of the L axles of the vehicle. Especially with trucks having three or more than three axles this leads to increased costs, which is a disadvantage.
Now, it is the object of the present invention to improve a method and a device of the before-mentioned kind so that the number of trigger transmitters required is smaller than the number of associated axle positions of the vehicle.
The invention achieves this object in that the number n of the trigger transmitters arranged on the vehicle is smaller than the number A of the axle positions,
that each axle position of the vehicle is associated to a triggering range of at least one of the n trigger transmitters,
that the trigger transmitters are so arranged and/or configured that at least one axle position is associated to the triggering range of at least two trigger transmitters,
that the identifiers of the electronic wheel units that respond to a trigger signal of a particular trigger transmitter are registered by the at least one receiving antenna and are passed on to the electronic receiver and evaluation unit, and
that the electronic evaluation unit calculates the axle position of a given electronic wheel unit based on the axle formula of the vehicle.
The invention achieves the objection also by a device for allocating first transmitters, which can be triggered, of a tire monitoring system, especially of a tire-pressure monitoring system, has a wheel unit comprising a sensor, a first transmitter and a sending antenna on each of N wheels arranged on L axles of a vehicle according to a predetermined axle formula, further has at least one receiving antenna on the vehicle body associated to the first transmitters, and an electronic receiver and evaluation system connected to the at least one receiving antenna, wherein allocation of the first transmitters to a defined axle position of the vehicle is effected by allocating to the respective first transmitter an identifier characteristic of the particular wheel, by emitting data telegrams, which contain the identifier, in response to a triggering action of second transmitters of the device which serve as trigger transmitters, and by passing on such data telegrams to the central electronic receiver and evaluation system. The trigger transmitters are so arranged and/or configured that at least one axle position is arranged in a triggering range of each trigger transmitter, that at least one axle position is associated to the triggering range of at least two trigger transmitters, and based on the axle formula of the vehicle, the electronic evaluation system calculates the axle position of a given electronic wheel unit by evaluation of the identifiers of the electronic wheel units responding to trigger signals of a given trigger transmitter.
On vehicles having at least three axles the invention advantageously allows allocating an electronic. wheel unit to a given axle position with the aid of a number of trigger transmitters smaller than the number of the axle positions. Such a feature advantageously leads to a significant reduction in costs.
An advantageous further development of the invention provides for level evaluation of the data telegrams emitted by the individual electronic wheel units. It is an advantage of that feature that it permits easily a spatial resolution of the various wheel positions of any axle position even if multiple tires exist at a given axle position, as is the case for example with twin tire systems.